Adequate and reliable braking for large vehicles, particularly tractor trailer vehicles, is assisted by devices known as engine brakes or engine compression brakes. An engine brake system utilizes the energy required to compress air in the cylinders of the engine to brake the vehicle. The drag put on the drive line by the engine when placed in the compression braking mode can serve to slow the vehicle more rapidly, when used in conjunction with the disc or drum brakes of the vehicle.
With the advent of electronic controls for use with internal combustion engines, the sophistication of control strategies increases. Specifically, when an engine control module or ECM is responsible for monitoring a host of parameters in supplying a variety of control signals to various devices, the ECM should prevent operation of engine compression braking when certain operating conditions exist.
One known engine brake controller device is shown in Meistrick et al., U.S. Pat. No. 4,664,070. The device disclosed therein includes a compression release-type engine retarder having a hydro-mechanical valve actuating mechanism operated by an electronic controller which responds to throttle position, actuation of the brake pedal, and other manual or automatic control or inputs. Other patents showing electrical controllers for operating compression release engine retarding systems include Meistrick, U.S. Pat. No. 4,592,319, and Sickler, U.S. Pat. No. 4,572,114.
Tart, Jr. et al., U.S. Pat. No. 4,742,806, discloses an engine braking system including an on/off switch and switches connected to other parameters such as clutch throttle position which, when in a favorable position, allow the system to operate, but when in an unfavorable position, the system is disabled. Furuhashi, U.S. Pat. No. 4,401,073, Matsunaga, U.S. Pat. No. 4,640,241, and Gravestock, U.S. Pat. No. 4,655,187 disclose electronic fuel control systems which include various inputs and outputs. Muir, U.S. Pat. No. 3,525,317, discloses a multiple-position switch actuated by a throttle pedal so that the position of the throttle pedal provides actuation in a multiple stage fashion of the engine compression braking system disclosed therein.
A control strategy for preventing operation of engine braking except when certain operating conditions and parameters are satisfied will provide more efficient and safer operation of engine braking.